1. Field of the Invention
The invention relates to belt or chain conveyors and, more specifically, to means and methods for converting roller conveyors into belt or chain conveyors.
2. Description of Related Art
Roller conveyors are commonly used, especially in the package handling industry, to provide a solid conveying surface for a variety of materials. Typical roller conveyors include a steel, galvanized, or aluminum frame with parallel side walls. An array of cylindrical rollers is supported between the side walls. Spring-loaded shafts extending from the ends of the rollers rest in openings in the side walls spaced to provide standard roller centers, such as 1.5 inches or 2 inches and their multiples. The topmost portions of the rollers lie in a conveying plane. Packages or other products placed on the conveying plane span two or more rollers. In the simplest of roller conveyors, packages are transported by gravity when the conveying plane is inclined or by a push when the conveying plane is horizontal. The momentum of the packages contacting a roller causes the roller to rotate and transport the package to the adjacent downstream roller. In powered roller conveyors, a rubber or fabric belt frictionally drives one or more of the conveying rollers to transport packages. Because of their simple construction, roller conveyors are an inexpensive means for conveying packages.
But roller conveyors have shortcomings. First, the roller bearings wear over time, which causes a roller to roll less easily or to freeze completely. Second, the mounting holes for the roller can wallow out, which can cause the rollers to assume cocked orientations relative to each other and to the conveying plane. Third, as they age, roller conveyors can become noisy. Fourth, because passive horizontal roller conveyors depend on a push to get a package rolling, there is no guarantee that the package will make it to its destination without getting stranded.
To meet changing conveyance demands, motor-driven belt or chain conveyors often replace roller conveyors. Motor-driven belt conveyors are less noisy, avoid stranding packages, and are especially helpful in transporting high volumes of packages. Because the roller conveyor is already in place, using as much of it as possible to support the replacement belt conveyor is advantageous. In many cases, a belt is merely installed on the roller conveyor frame with the rollers acting as a carryway support for the belt. One problem with this solution is the noise generated by the belt bouncing up and down on the undulating and intermittent support surface provided by the rollers. For that reason, the rollers are often removed and replaced by a metal support structure positioned between and supported by the side walls of the roller conveyor frame. But it takes a lot of time and effort to remove the rollers and construct, fit, and install the support structure.
Clearly there is a need for a simple and quick way to convert a roller conveyor into a motor-driven belt or chain conveyor.